This application claims priority from Korean Patent Application No. 2002-20908, filed on Feb. 2, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to solar cells, and more particularly, to dye-sensitized solar cells including polymer electrolyte gel.
2. Description of the Related Art
As the buried amount of fossil fuel is exhausted, it has been tried to convert solar energy into electric energy using semiconductors and it has been considered as a promising field, industrially. In addition, as policies of restricting the generation of carbon dioxide are established, solar cells that generate electricity without generating contaminants provide solutions for the needs of saving environment and generating energy.
A representative example of conventional dye-sensitized solar cells was provided by Gratzel et al. from Switzerland, in 1991. Gratzel et al. disclosed a photoelectric chemical solar cell using an oxide semiconductor which is formed of photosensitive dye particles and nanocrystalline titanium dioxide. The solar cell provided by Gratzel et al. has an advantage of being manufactured at a low cost. Conventional dye-sensitized solar cells including nanocrystalline oxides are formed of nanocrystalline oxide semiconductor cathode, platinum anode, dye coated on the cathode, and oxidation/reduction electrolyte using an organic solvent. In such a conventional dye-sensitized solar cell including the electrolyte, which is obtained from the organic solvent, the electrolyte solvent is likely to volatilize from the solar cell when the external temperature of the solar cell is increased due to the sunbeams. Accordingly, the conventional dye-sensitized solar cell is unstable and cannot be utilized.
The present invention provides dye-sensitized solar cells that provide an energy conversion efficiency of the same level as that of a conventional dye-sensitized solar cell and provide stable photoelectric chemical characteristics regardless of changes in an external environment, such as external temperature of the solar cells, by minimizing the possibility of volatilization of a solvent included in polymer electrolyte gel.
According to an aspect of the present invention, there is provided a dye-sensitized solar cell comprising a semiconductor electrode, an opposed electrode, and a polymer electrolyte gel interposed between the semiconductor electrode and the opposed electrode while including poly(vinylidene fluoride) (PVDF) polymer or the copolymer thereof.
The polymer electrolyte gel may be formed of a N-methy-2-pyrrolidone solvent and the PVDF polymer or the copolymer thereof which is dissolved in the solvent to a predetermined amount. Alternatively, the polymer electrolyte gel may be formed of a 3-methoxypropionitrile (MP) solvent and the PVDF polymer or the copolymer thereof which is dissolved in the solvent to a predetermined amount. It is preferable that the polymer electrolyte gel is formed by mixing 3 to 20 wt % of the PVDF polymer of the copolymer thereof based on the weight of the solvent.
The semiconductor electrode is formed of a transparent conductive substrate and a transition metal oxide layer, which is coated on the transparent substrate. The semiconductor electrode further comprises a dye molecular layer, which is chemically adsorbed to the transition metal oxide layer. The dye molecular layer may be formed of ruthenium complex.
The transition metal oxide layer is formed of nanocrystalline titanium dioxide.
The opposed electrode is formed of a transparent conductive substrate and a platinum layer, which is coated on the transparent substrate.
The dye-sensitized solar cell according to the present invention improves the photo voltage compared to the conventional solar cell and reduces the volatility of the solvent while not lowering the energy conversion efficiency. Thus, the dye-sensitized solar cell is stable for a long time regardless of changes in the external conditions, such as increase of the external temperature of the solar cell due to the sunbeams.